FIGS. 1 and 2 show a conventional built-in function type wiring apparatus. In these figures, an electronic circuit unit 11 is mainly composed of a functional circuit 11a for transmitting signals between wire harnesses. A junction block 12 has therein a bus bar circuit 12a mainly having a branch function. The unit 11 and the block 12 are respectively provided with a connector 13 for connecting the block, and a connector 14 for connecting the unit, and are electrically connected to each other through the connectors 13 and 14. A plurality of connectors 16, 16', etc., are disposed in a casing of the block 12 to functionally connect a fuse F and an external wire harness W. A plurality of connectors 15, 15', etc., are also disposed in the unit 11 to directly connect an external wire harness W'.
The functional circuit mentioned above means a circuit for controlling the operations of electrical devices mounted on a vehicle, for example, by input or output signals from various kinds of switches, sensors, etc. The functional circuit may be constituted by an alarm circuit for giving an alarm when a door is not completely closed, a wiper control unit circuit, etc. FIG. 2 shows a control section 17 for embedding elements and electronic parts such as transistors, LSI, MCP, relays, timers, etc., which are needed to control the circuit.
In the conventional wiring apparatus mentioned above, the plurality of connectors 15, 15', etc., are also disposed in the unit 11 to directly connect the external wire harness W', thereby causing the following problems:
(1) It is necessary to dispose a bus bar(through circuit) 12a' irrespective of the control section 17, as in the connector 15, for example, thereby increasing the number of parts such as connecting terminals and connector housings on the side of the unit 11, and increasing the cost of the apparatus. PA1 (2) The through circuit 12a' and a circuit 11b for inputting and outputting signals connected to the control section 17 are disposed in a mixed state in the connectors 15' and 15" so that the structure of an internal circuit of the unit 11 is made complicated and a branch connection designated by reference numeral J is particularly made complicated. PA1 (3) In the wiring of a vehicle, the plurality of connectors 15, 15', etc., must be connected to the unit 11, in addition to the connection between the junction block 12 and the electronic circuit unit 11, thereby increasing the number of assembly operations.